In residential and commercial building construction it is necessary to connect the base of a porcelain toilet to a drain pipe in a secure and water tight manner that meets all plumbing codes applicable in the local jurisdiction. The most common way of achieving this connection is to utilize a so-called closet flange. See for example U.S. Pat. Nos. 3,181,585; 3,339,215; and 4,090,267. The typical closet flange is flat and round and includes a pair of semi-circular diametrically opposed key-shaped slots which allow for the insertion of bolts that are used to tighten the base of the toilet to the flange. Early closet flanges were made of cast iron and were connected to cast iron drain pipes. Modem closet flanges are typically made of ABS or PVC plastic and include a main cylindrical body portion that is solvent welded to a drain pipe made of a similar plastic and an attachment flange portion that extends radially from the upper end of the main cylindrical body portion and is bolted to the base of the toilet.
A problem continually faced by plumbers involves the prevention of clogging of toilet drain pipes during construction owing to the fact that these pipes are usually installed long before the toilet is mounted over the same. Sawdust, nails, wood chips, putty, screws, tape, paper, and even blocks of wood fall into the open upper ends of the drain pipes and cause major blockages after the newly completed building is occupied. Some plumbers use cloth, plastic or tape as temporary coverings. However, since most plumbing codes require pressure testing of the drain system to detect leaks, it is necessary to provide an air tight seal. Mechanical and pneumatic test plugs have been used with some success, but when the test is completed the drain pipe remains unsealed. Since the upper end of the pipe is at floor level, debris naturally falls into the drain pipe. Gluing on a pressure test cap is time consuming and its removal is difficult.
U.S. Pat. No. 5,115,554 of Fell, Sr. discloses a closet flange with a screw plug for sealing its axial bore. This requires pipe threads to provide an airtight seal, and such threads are not practical to form during injection molding of a single unitary closet flange. Therefore closet flanges have been molded with integral knockouts.
U.S. Pat. No. 4,827,539 of Kiziah discloses a closet flange with an integral knockout plug 10′ which can fall well down into the drain pipe during attempted removal of the plug making it extremely difficult to retrieve
U.S. Pat. No. 5,377,361 of Piskula discloses a closet flange with a knock out element that has a diameter larger than an internal diameter of a lower portion of the cylindrical body portion to prevent the knock out element from falling down into the drain pipe.
It would therefore be desirable to provide a plastic closet flange with a main cylindrical body portion that could be solvent welded around the outside of a standard smaller size, e.g. a three inch diameter plastic drain pipe, or within the inside of a standard larger size, e.g. a four inch diameter plastic drain pipe, and which is configured so that its knockout cannot fall down inside either the smaller or larger size of drain pipe.